Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/60—Compositions for stimulating production by acting on the underground formation
  • C09K8/82—Oil-based compositions
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/02—Well-drilling compositions
  • C09K8/04—Aqueous well-drilling compositions
  • C09K8/06—Clay-free compositions
  • C09K8/08—Clay-free compositions containing natural organic compounds, e.g. polysaccharides, or derivatives thereof
  • C09K8/10—Cellulose or derivatives thereof
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S507/00—Earth boring, well treating, and oil field chemistry
  • Y10S507/925—Completion or workover fluid

Definitions

• the present invention relates to the preparation and use of novel viscosifier systems which are added to drilling and completion fluids used in oil and gas drilling operations. More particularly the present invention relates to solar solvent-in-oil emulsions which are specially prepared and mixed with high concentrations of conventional viscosifiers increasing their effectiveness.
• drilling and completion fluids are used in the drilling of oil and gas well. These fluids are essential to drilling operations as they perform a variety of important functions. For example, drilling fluids cool and lubricate drill bits and pipe; prevent damage to producing formations; suspend and remove cuttings from wells; and generally clean out wells.
• the most effective drilling fluids consist of concentrated salt solutions such as sodium chloride or calcium chloride. These salt solutions or brines may be used alone when drilling shallow wells or in combination with insoluble weighting materials for deep well drilling. In order to maintain the high formation pressure of deep wells, insoluble weighting materials have been added to the drilling solutions. Unfortunately, use of these insoluble weighting materials can present serious problems during completion operations.
• the insoluble materials can reduce or destroy the permeability of the producing zone by filtering into the formation and impeding the flow of the oil and gas.
• solids-free salt and water solutions which have density ranges between 10 and 19.2 pounds per gallon (“lb./gal.") have been developed for deep well drilling. These brines generally require the addition of viscosifiers and other additives to be thoroughly effective. By adding viscosifiers to the brine solutions their ability to suspend and remove cuttings from the well is increased and significant loss of fluids to the formation is prevented.
• natural polymers such as guar gum, hydroxypropyl guar, xanthan gum, carboxymethyl cellulose and hydroxyethyl cellulose can be used as viscosifiers when brine solutions are in the 10-19.2 lb./gal. density range. See also Chatterji J. and Borchart J. K.; J. Pet. Tech. 2042-2056 (1981). By far the most commonly used viscosifier for brines in the 10-19.2 lb./gal. density range is hydroxyethyl cellulose or "HEC".
• HEC and other hydrophilic polymers to brines is very important. If the dry polymer is added to the brine solution without manipulation, the interior of the polymer will not hydrate and the polymer will be prevented from effectively viscosifying the brine.
• U.S. Pat. No. 4,459,214 and U.K. Pat. No. 2,086,923B disclose a partial resolution to the solvation problem. These patents propose addition of polar organic solvents such as ethylene glycol, propylene glycol and dimethylformamide to the polymer-brine mixtures to increase solvation of the polymer and, therefore, its ability to viscosify brine solutions.
• the present invention has for its primary object obtaining a solution to the solvation problem without the necessity of using high temperatures, high shear or long mixing times, while permitting a high concentration of polymer to be dissolved in the brine solutions.
• Another object of the present invention is to create a "pourable" viscosifier system.
• a further object of the invention is to produce a viscosifier system with a minimum shelf live of 6 months which has minimal phase separation.
• An additional object of the invention is to create a viscosifier system which yields a minimum funnel viscosity of 200 sec at a concentration of 10 lb./bbl., or greater, within 60 min. at room temperature and low shear.
• Another object of the invention is to develop a viscosifier system which is safe to use in all drilling and completion operations with no adverse effects.
• the present invention relates to viscosifier compositions which can effectively viscosify alkali and alkaline earth metal and zinc halide brines in the density range of 10-19.2 lb./gal. without heating, high shear or long mixing times.
• These systems comprise in the preferred embodiment about 20-35 wt. % viscosity inducing hydrophilic polymer; about 30-55 wt. % mineral oil; about 3-6 wt. % of one or more oil soluble, nonionic surfactants; about 10-40 wt. % of one or more polar solvents emulsified in the mineral oil; and about 5-15% of one or more diluting agents and yield minimal funnel viscosities of 200 sec. at a concentration of 10 lb./bbl. within 60 min. at room temperature and low shear.
• viscosified brines comprising a viscosityingly effective amount of the foregoing viscosifying composition incorporated in a 10.0 to 19.2 lb./gal. aqueous solution of one or more alkali and alkaline earth metal and zinc halides.
• Suitable halides include sodium chloride, sodium bromide, lithium bromide, calcium chloride, calcium bromide, zinc bromide and zinc chloride.
• the present invention encompasses the down-hole use of the viscosified brines of this invention in the completion and work over of oil and gas wells.
• the present invention discloses liquid viscosifier systems capable of viscosifying concentrated aqueous brines in the density range of 10-19.2 gal./lb. or 1.05 to 2.30 g/cc.
• These liquid viscosifier systems comprise mineral oil, one or more surfactants, one or more polar solvents, one or more diluting agents and a viscosity inducing hyrophilic polymer, most desirably in the following weight percentages:
• Bentone clay has been found to make the composition more pourable and, therefore, easier to use.
• composition can be made with any white mineral oil in the viscosity ranges of 70-350 SSU at 100 degrees Fahrenheit.
• surfactants used in the composition should be oil-soluble and nonionic.
• Nonlimiting examples of surfactants include alkylaryl polyether alcohols such as octyl- or nonyl phenol based alkylaryl polyether alcohols and polyether compounds such as block copolymers of propylene and ethylene oxides and polyethylene glycol fatty acid esters.
• Polar solvents which may be used in the composition include, but are not limited to, any organic alcohols, aliphatic glycerols, and N-methylpyrrolidones in which hydrophilic polymers are soluble and water. Any long chain aliphatic alcohol such as octanol may serve as a diluting agent for the composition. Finally, any viscosity inducing hydrophilic polymer which is soluble in polar solvents and increases the viscosity of brines such as cellulose, carboxymethyl cellulose and hydroxyethyl cellulose or HEC may be used as the hydrophilic polymer of the composition. HEC is preferred in accordance with the present invention.
• the viscosifier composition may be prepared by first thoroughly mixing the mineral oil with the surfactant. A mixture of polar organic solvents and diluting agents is then added over a 3 minute period and the resulting emulsion is agitated by a propeller stirrer, initially at 250 rpm and as the emulsion increases in viscosity at 700 rpm. When the mixing is complete the resulting emulsion is stirred by propeller stirrer at 700 rpm for an additional 5 minutes. Bentone Clay may be added to the emulsion to make the overall liquid viscosifier system more pourable. Dry polymer is then slowly added to the emulsion in order to form a good suspension. Other mixing procedures may be used, if desired.
• Suitable brines which may be viscosified in accordance with this invention include aqueous solutions containing substantially any alkali and alkaline earth metal and zinc halides.
• Such brines may be formulated with one or more of the following salts: sodium chloride, sodium bromide, lithium bromide, calcium chloride, calcium bromide, zinc bromide and zinc chloride provided at a density lying in the range of about 10.0 to 19.2 pounds per gallon.
• the viscosifier may in turn be admixed with a brine solution in any convenient way to provide the desired viscosified brine.
• a brine solution in any convenient way to provide the desired viscosified brine.
• the viscosifying composition is provided in the brine at a level of about 0.2-10.0, preferably about 0.5-2% by weight of the overall composition.
• the viscosifiers of this invention are effective at substantially any pH exhibited by the alkali and alkaline earth metal and zinc halide brines of this invention. Thus, pH does not pose a limitation on the effective utilization of the viscosifiers of this invention.
• a liquid viscosifier system for single salt brines such as sodium chloride, calcium chloride, sodium bromide, lithium bromide and calcium bromide was prepared by first thoroughly mixing 2.0 wt% of "X-207" and 1.0 wt% of "X-45", (alkylaryl polyether alcohol nonionic surfactants commercially available from Rohm and Haas) with 52.5 wt% Semtol-100 Mineral Oil (commercially available from Witco Chemical). A mixture of 3.5 wt% glycerol, 3.5 wt% ethylene glycol and 7.0 wt% water was added over a three minute period and the resulting emulsion was agitated at 250 rpm by a propeller stirrer.
• X-207 alkylaryl polyether alcohol nonionic surfactants commercially available from Rohm and Haas
• Semtol-100 Mineral Oil commercially available from Witco Chemical
• the agitation speed was raised to 700 rpm.
• the emulsion was then stirred for an additional 5 minutes at 700 rpm.
• 0.5 wt% of Bentone Clay from Southern Clay Products, Inc. was added to the emulsion to make the emulsion more pourable.
• 30.0 wt% of dry HEC was added slowly to the emulsion and the emulsion was mixed.
• Fann viscometer a type of rotational viscometer, was used to measure the viscosity of the viscosified brine solution. Fann viscometers operate under steady-state conditions so that close approximations of how a fluid would behave in actual industrial circumstances, i.e., stirring, dispersing, pumping, metering, may be obtained. Fann viscometers are widely used for routine evaluations and quality-control measurements. A Fann-35 reading of 150 at 300 r.p.m. indicates that a solution has a sufficient viscosity to act as a fluid loss agent in drilling or completion operations.
• the Marsh funnel viscosities of the viscosified brine solution were measured.
• the procedure for measurement of Marsh Funnel Viscosities is described in the API RP 13B Publication (1976, P.S. ), as follows: "The Marsh funnel is dimensioned so that, by following standard procedures, the outflow time of one quart (945 cu. cm.) of fresh water at a temperature of 70 +/-5 degrees Fahrenheit is 26.0+/-0.5 sec.”
• brine solutions must exhibit funnel viscosities of 200 sec. or better to be effective as pills for stopping the fluid loss to the formation.
• Table I presents the funnel viscosities and Fann-35 readings for the viscosifier of Example I provided in in various single salt solutions.
• Table II presents the Rheology data for the Example I viscosifier in single salt solutions. These data demonstrate the plasticity of fluids at high pressures as in deep well formations.
• the viscosified fluids behave according to the Bingham-plastic model.
• a Bingham fluid is similar to a Newtonian fluid in that both exhibit straight-line relationship between shear stress and shear rate.
• the Bingham-plastic fluid has an intercept on the shear-stress axis, which is called the yield point (YP).
• the slope of shear stress versus shear rate line is the plastic viscosity (PV).
• the apparent viscosity of Newtonian and plastic fluids is determined by dividing the Fann-35, 600 r.p.m. reading by 2. For a Newtonian fluid (one in which a shear stress versus shear rate plot gives a straight line through the origin), the apparent viscosity is equal to the plastic viscosity. For plastic fluids, such as completion fluids, the apparent viscosity is of limited value because the slope of flow curve cannot be defined by measuring the shear rate at only one speed.
• the major shortcoming of using the Bingham plastic model is that it only describes the fluid flow over a very narrow shear rate range of 600 and 300 r.p.m.
• the shear rate ranges encountered in a typical drilling situation are between 3 and 100 r.p.m. Consequently, the Bingham plastic model may not accurately describe fluid rheological characteristics in all drilling situations.
• a second liquid viscosifier system was prepared using a procedure identical to that of Example I.
• the formulation for the liquid viscosifier system of Example II is slightly different than the Example I formulation in that the HEC concentration is decreased and the polar organic solvent concentration is increased.
• the Example I formulation contains 30 wt. % of HEC, it does not viscosify two-salt calcium fluids effectively. Because of the small concentration of the polar solvents in the Example I formulation, most of the HEC is not solvated; hence, it cannot viscosify two-salt fluids.
• the concentration of the polar solvents was increased in order to solvate more HEC. Therefore, the concentration of HEC was decreased in order to prevent gel formation.
• the formulation for the Example II viscosifier is given in Table III.
• Example II formulation is capable of viscosifying all CaBr 2 and CaCl 2 fluids but is not as effective as Example I, in viscosifying single-salt brines.
• Table V presents the rheology data for the viscosifier of Example II.
• Example III A liquid viscosifier system for single salt solutions and is prepared according to the procedure of Example I. The ratio of mineral oil to polar organic solvent has been changed from that in Example I. The formulation for Example III is given in Table VI.
• Example III exhibits higher rheology for single-salt fluids (compare Tables I and VII). A concentration of 10 lb/bbl of viscosifiers has been used as a basis for comparing the results.
• a liquid viscosifier was prepared using the procedure described in Example I.
• the ratio of polar solvents to mineral oil or non-polar solvent was changed in order to solvate more HEC. Additionally, the concentration of HEC was decreased to prevent gel formation due to the high concentration of water in the system.
• the Example IV liquid viscosifier was designed to viscosify all the completion fluids in the density range from 10.0 to 19.2 lb./gal.
• the formulation of Example IV was similar to Example II, except that ethylene glycol was replaced with octanol and HEC content was increased by 5 wt. %.
• the Example IV liquid viscosifier in addition to being more effective than the liquid viscosifier of Example II, is also more pourable.
• the relative weight percents for this liquid viscosifier are given in Table IX.
• the fluid flow characteristics for completion fluids are non-Newtonian. Hence the effective viscosities encountered at a given shear rate need to be considered.
• the Fann-35 readings can be converted to viscosity by using certain conversion factors. For example, for CaCl 2 fluids viscosified with 10 lb./bbl. of Example IV (Table X), the actual viscosities at 100 rpm and 3 rpm are 480 cp and 4300 cp, respectively.
• Example V The procedure for preparing another liquid viscosifier is identical to that of Example I. Although the liquid viscosifier of Example IV is effective for both single- and two-salt fluids, two hours of mixing is required to achieve an acceptable viscosity in the two-salt fluids. Further, in order to increase the solvation of HEC in the system, 15 wt. % of N-methyl-2-pyrrolidone was added and the concentration of HEC was decreased. The Example V liquid viscosifier is designed to viscosify both single and two-salt solutions containing calcium and zinc ions in the density range of 11.6 to 19.2 lb./gal. The weight percents for this viscosifier are given in Table XII.
• Example V liquid viscosifier can viscosify all single- and two-salt calcium and zinc fluids in one hour to about 200 cp at 300 rpm.
• ⁇ is the shear stress
• ⁇ the shear rate
• K is a proportionality constant
• n is a measure of deviation of a fluid from Newtonian behavior.
• the fluid is Newtonian, with K being equal to viscosity, ⁇ .
• Equation (1) can be presented in the following form:
• Table XIV gives the apparent viscosity, plastic viscosity, and yield point using the data given in Table XIII.
• Example III and Example V are the most effective viscosifiers for fluids in the density range of 10.0 to 19.2 lb./gal. although the others may be used.
• the liquid viscosifier of Example III should be used for sodium chloride, calcium chloride, and sodium bromide fluids (10.0 to 12.5 lb./gal. density range), whereas the liquid viscosifier of Example V is most effective in calcium chloride, calcium bromide, calcium bromide/calcium chloride and zinc bromide/calcium bromide fluids (10.0 to 19.2 lb./gal. density range).
• Tables XV and XVI present the rheology data for different fluids viscosified with 5.0, 7.5, and 10.0 lb/bbl of the liquid viscosifier of Example III and the liquid viscosifier of Example V.
• Tables XV and XVI provide a guideline for choosing appropriate viscosifier concentration for a particular application. As these data indicate, the range of 5 to 10 lb/bbl concentration of the liquid viscosifiers of Example III and Example V are sufficient for most applications encountered in drilling and completion operations.
• the viscosifier systems of the present invention may be compared with LIQUI-VIS and BROMI-VIS, commercially available HEC viscosifiers from NL-Baroid.
• LIQUI-VIS is believed to be a 25 wt. % HEC in diesel oil; BROMO-VIS is 20 weight percent in isopropanol.
• LIQUI-VIS is only moderately effective in sodium chloride, calcium chloride, and sodium bromide fluids (density range of 10.0 to 12.5 lb./gal.). To achieve any viscosification in sodium chloride and sodium bromide fluids, the pH of LIQUI-VIS must be adjusted to 8-9 prior to addition of the viscosifier. LIQUI-VIS does not viscosify calcium bromide and calcium bromide/calcium chloride fluids at all.
• BROMI-VIS only viscosifies calcium bromide and calcium bromide/calcium chloride fluids and not sodium chloride or sodium bromide solutions. It also forms a hard gel making its utilization somewhat difficult.
• OSCA-VIS a viscosifier commercially available from Oilfield Service Corporation of America, contains 10 wt. % HEC solvated with ethylene glycol. At 10 lb/bbl, it is only moderately effective in calcium bromide/calcium chloride fluids. To make OSCA-VIS effective in sodium chloride and sodium bromide fluids, it is necessary to adjust the pH to 8-9 and to use concentrations of 30-40 lb/bbl of viscosifier.
• Table XVII presents the comparative rheology data for brines viscosified with 10 lb/bbl of the viscosifier systems of the present invention and commercial viscosifiers. From Table XVII it is clear that the liquid viscosifiers of Example III and Example V are superior to other products.
• Example III Only after pH adjustment can LIQUI-VIS viscosify NaCl and NaBr fluids.
• the liquid viscosifier of Example III viscosifies NaCl and NaBr without any pH adjustment and the viscosities obtained are higher than those achieved with other products.
• BROMI-VIS is not effective in CaCl 2 fluid. Although OSCA-VIS and LIQUI-VIS can viscosify CaCl 2 , the values are significantly lower than those obtained with Example III.
• Example V exhibits higher rheology than all the other viscosifiers.
• Clear drilling and completion fluids also have utility in wells which contain subterranean carbonates and sulfates.
• Unfortunately use of calcium ion containing clear fluids in these types of wells has resulted in formation damage caused by precipitation and calcium carbonate and calcium sulfate from the clear fluids.
• sodium bromide fluid has been used in place of calcium ion containing fluids in relatively shallow wells where high formation pressures are not encountered.
• sulfate and carbonate containing wells have been discovered which require use of drilling and completion fluids with fluid densities well above those of sodium bromide (i.e., in the 14-20 lb./gal. density range).
• calcium-free fluids for use as oil field completion, packer and perforating media.
• These calcium-free fluids are formulated by mixing zinc bromide or zinc chloride with alkali metal halides (NaCl, NaBr, KCl, KBr, LiCl, and LiBr) and water.
• alkali metal halides NaCl, NaBr, KCl, KBr, LiCl, and LiBr
• these calcium-free fluids are formulated by mixing zinc bromide with alkali metal bromides (NaBr, KBr and LiBr) and water.
• These fluids have densities in the range of 8.5 to 21.0 lb./gal. and pH's in the range of 1.0 to 7.5.
• the concentration ranges of zinc bromide and alkali metal bromides in these fluids are 4-77 wt.% and 2-55 wt.%, respectively.
• the calcium-free fluids disclosed in the Ser. No. 892,155 patent application may be easily viscosified with the viscosifier of Example V.
• Tables XX and XXI present funnel viscosity and rheology data for different zinc bromide/sodium bromide and zinc bromide/potassium bromide fluids viscosified with the liquid viscosifier of Example V.
• Example V viscosifier at a concentration of 15 lb./gal. is an effective viscosifier for the zinc ion-containing calcium-free fluids in the density range of 15.0 to 19.0 lb./gal.
• Zinc bromide/calcium bromide fluids in the density range of 15.0 to 16.5 lb./gal. are difficult to viscosify, apparently because of structural changes in the solvent and solute caused by the different concentration ratios of halide to zinc ion.
• Tables XIX and XX clearly indicate the effectiveness of Example V viscosifier in calcium-free fluids. Therefore, calcium-free fluids viscosified with Example V offer new viscosified fluids in the density range of 15.0 to 16.5 lb./gal.

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• 1986
  • 1986-09-29 US US06/913,415 patent/US4762625A/en not_active Expired - Fee Related
• 1987
  • 1987-09-10 WO PCT/US1987/002305 patent/WO1988002434A1/en not_active Ceased
  • 1987-09-10 EP EP87906359A patent/EP0289529B1/de not_active Expired - Lifetime
• 1988
  • 1988-05-27 NO NO882350A patent/NO175724C/no unknown

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